Actual mileage vs computer readout
#1
Actual mileage vs computer readout
I know there have been a number of posts regarding this subject, but I have just completed my own 'research' on the subject.
To start with, I reset the computer at a fill-up. Filled up till auto shut off, then rounded it to the nearest even amount.
Did the same thing over the course of a month, using the same station and same pump each time. Calculated mileage by hand (okay, used a calculator) each time.
Results -
Computer read between 15.0 and 15.8 each tank
Manual calculations indicated between 15.0 and 15.6
Filled up 6 times over this period, and twice the computer and manual results were exact. Largest discrepancy was 0.3 MPGs
All in all, I would say the computer does a pretty fair job of telling me what my mileage is.
As an fyi, 2003 truck is totally stock, no fuel additives used (although it's starting to get cold so will use them now). Non synthetic oil.
To start with, I reset the computer at a fill-up. Filled up till auto shut off, then rounded it to the nearest even amount.
Did the same thing over the course of a month, using the same station and same pump each time. Calculated mileage by hand (okay, used a calculator) each time.
Results -
Computer read between 15.0 and 15.8 each tank
Manual calculations indicated between 15.0 and 15.6
Filled up 6 times over this period, and twice the computer and manual results were exact. Largest discrepancy was 0.3 MPGs
All in all, I would say the computer does a pretty fair job of telling me what my mileage is.
As an fyi, 2003 truck is totally stock, no fuel additives used (although it's starting to get cold so will use them now). Non synthetic oil.
#2
I believe if you reset the computer EVERY time, the mileage will check out closer to actual. However, if you do not reset the comuter, it will eventually create a larger spread compared to actual due to the fact that the computer is averaging your fuel economy for the total amount of miles & usage since the last reset.
#3
I have a spreadsheet containing every fill up I have ever done, with calculated MPG. The lie-o-meter is usually 1-2.5 MPG off, consistently. After disconnecting the battery, it got worse. My driving is not consistent, but then I'm not sure if that matters. I only use it as a rough gauge. Last time I filled up, it said 18.0 and I calculated just over 16. Granted- I have slightly larger tires, so the error is closer to 1 MPG than 2 on that tank of gas.
#4
Similar results
I have seen similar results with my 04 as Tekrep reported using the same procedure. But if I run say half a tank purely on the highway and run the rest of the tank in the city, it seems as though the actual mileage calculated by hand is about 1 mpg off from the computer.
Here's some food for thought. Assume that you travel 480 miles and get 15 mpg. That would translate to 32 gallons of fuel used. Now if you squeeze an extra gallon of fuel into the tank either to round up to the next round dollar figure or to just top off the tank, your calcuated mileage drops to 14.5 MPG. My point is that very small changes in the amount of fuel you pump translate into larger changes in the calculated fuel mileage.
Here's some food for thought. Assume that you travel 480 miles and get 15 mpg. That would translate to 32 gallons of fuel used. Now if you squeeze an extra gallon of fuel into the tank either to round up to the next round dollar figure or to just top off the tank, your calcuated mileage drops to 14.5 MPG. My point is that very small changes in the amount of fuel you pump translate into larger changes in the calculated fuel mileage.
#5
My 2 Centavos
I fill up at a station which, after hours, only allows $60.00 worth of fuel per use. I needed to fill up and only put in the $60.00, (it did not fill all the way up). I noticed my computer showed 20 MPG after about 50 miles on the highway. Prior to this "fill up", it indicated about 17 MPG. Can anybody comment about this?
#6
Originally Posted by Cholo
I fill up at a station which, after hours, only allows $60.00 worth of fuel per use. I needed to fill up and only put in the $60.00, (it did not fill all the way up). I noticed my computer showed 20 MPG after about 50 miles on the highway. Prior to this "fill up", it indicated about 17 MPG. Can anybody comment about this?
The bottom line is, if you really want to know how your truck is doing, and want to catch a "trend shift", keep an electronic record (Excel spreadsheet) of all fill-ups. This will show you how it performs towing v. empty, and HWY v. City. It will also let you know if something has REALLY changed- many people think they are getting bad mileage, but it is a function of condition and driver input.
#7
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#8
Originally Posted by Tekrep
I have a spreadsheet containing every fill up I have ever done, with calculated MPG. The lie-o-meter is usually 1-2.5 MPG off, consistently. After disconnecting the battery, it got worse. My driving is not consistent, but then I'm not sure if that matters. I only use it as a rough gauge. Last time I filled up, it said 18.0 and I calculated just over 16. Granted- I have slightly larger tires, so the error is closer to 1 MPG than 2 on that tank of gas.
#9
Originally Posted by Ophus
I have been waiting to post on this same subject. The last 4 tanks where I have been tracking the mileage has shown the readout to be within 2 tenths every time. I wonder why some seem to work and others do not?
Claude
#10
#11
Originally Posted by beemr
I believe if you reset the computer EVERY time, the mileage will check out closer to actual. However, if you do not reset the comuter, it will eventually create a larger spread compared to actual due to the fact that the computer is averaging your fuel economy for the total amount of miles & usage since the last reset.
2839 Miles
165.0 Gals
17.2 MPG Calculated
17.8 MPG Computer
This seems close enough to use as a reference for the same type of driving.
As another interesting check I had my GPS on to check cumlative miles and speed. The GPS actually showed 2851 miles, so the Ford odometer seems pretty close. The speedometer varied, but always indicated one or two MPH faster than the GPS. This was good for me, as I like to set the cruise for 5 MPH more than posted .
Wayne
#13
#15
Fill to the neck
I have noticed that if I fill mine to the neck that the lie-o-meter reads higher than the calculated. I have assumed that this had something to do with the fact that I didn't fill to the top of the filler neck on the previous fill up. I'll have to try filling to the top of the filler neck for several fill ups to see if it makes a difference.